Field of the Invention
The present invention relates to an image capture apparatus and a method for controlling the same, and in particular relates to an image capture apparatus using an image sensor having pixels each including a plurality of photoelectric conversion units, and a method for controlling the same.
Description of the Related Art
An image sensor that includes pixels each configured such that light beams having passed through different partial areas of an exit pupil of an imaging optical system are received by separate photoelectric conversion units is known. Such pixels are used to acquire signals of two images (hereinafter, referred to as an A image and a B image) that have a parallax. Phase-difference detection-based focus detection is possible by obtaining a phase difference between the A image and the B image. Furthermore, it is also possible to generate a range image based on the A image and the B image.
As an application example of the A image and the B image, techniques are known in which amounts of defocus between the A image and the B image in respective small areas of a captured image are obtained and image processing according to the amounts of defocus is applied (Japanese Patent Laid-Open No. 2008-15754), and in which distribution of amounts of defocus is obtained and stored (Japanese Patent Laid-Open No. 2009-124313).
In order to calculate the amounts of defocus for respective small areas of a captured image, an image sensor needs to have a large number of pixels each including a plurality of photoelectric conversion units, as shown in FIGS. 2A and 2B. However, there may be the problem that a processing load for calculating the amounts of defocus increases, making it difficult to perform real-time calculation of the amounts of defocus particularly when a shooting interval is short as in shooting a moving image.
Furthermore, advanced image processing may be needed for acquiring the amount of defocus and distance information for each pixel more exactly. For example, it is common to obtain, as a phase difference or an amount of parallax between the A image and the B image, a phase difference (shift amount) having the highest correlation value, but in the case where a subject has a periodic texture, a plurality of different shift amounts have a high correlation value and thus it may be difficult to calculate a correct value. Furthermore, if there is an area that exists only in one of the A image and the B image, a phase difference or an amount of parallax with respect to this area cannot be obtained.
Accordingly, when an image capture apparatus needs to perform enormous calculation like this, real-time processing at the time of moving image shooting or continuous shooting is difficult with the processing power of the image capture apparatus. Furthermore, there may be a case where, due to a circuit size and the like, hardware for executing complicated processing cannot be mounted on the image capture apparatus. In such a case, the image capture apparatus needs to output image signals of the A image and the B image so that an external apparatus performs calculation of the phase difference or the amount of parallax, generation of a range image, or the like, or the image capture apparatus or the external apparatus needs to execute the same processing with respect to stored RAW data.
However, when image signals of the A image and the B image are output to the external apparatus, for example, when each pixel of the image sensor acquires the A image and the B image, it is necessary to transmit the amount of data that corresponds to a two-fold the number of pixels. Furthermore, the memory capacity needs to be saved also when the data is stored and then image processing is performed thereon. Therefore, a technique for reducing the amount of data that is to be transmitted or stored while enabling calculation of the amount of parallax is needed.